Effects of total lymphoid irradiation on SIV-infected macaques.

The identification of antiretroviral drugs that prevent, or delay for extended periods, progression of HIV-related disease has been of limited success. Because the number of HIV-infected people continues to increase, other therapeutic approaches must be tested. Using simian immunodeficiency virus (SIV)-infected macaques in a feasibility study, total lymphoid irradiation (TLI) was administered in fractionated doses to the supradiaphragmatic and then the infradiaphragmatic lymph nodes until a cumulative dose of 34.2 Gy was achieved in each field. During treatment and for more than 1 year of follow-up, the effects of TLI on various virological, hematological, and immunological parameters were evaluated and compared to those of similarly treated, uninfected macaques. Despite sustained low numbers of CD4+ lymphocytes (<100//g=m/I blood) during treatment, TLI was well tolerated, did not result in intercurrent infections, and more importantly, induced a transient decrease in viral burden and did not exacerbate d...